The present invention relates to electrical adapters and methods using such adapters. More particularly, the present invention pertains to employing a torque limiting apparatus with adapters for packaged integrated circuit devices (e.g., micro lead frame packages, micro lead chip carriers, quad flat no lead packages, and micro ball grid array packages, etc.) and methods for using such adapters.
Certain types of integrated circuit packages are becoming increasingly popular due to their occupancy area efficiency. In other words, they occupy less area on a target board on which they are mounted while providing a high density of contact terminals. For example, one such high density package type is a micro lead frame package. Generally, such packages contain an integrated circuit having its die bond pads electrically connected to respective conductive contact lead elements (e.g., lands) that are distributed on a surface of the package (e.g., the bottom surface of the package, for example, in an array).
A target printed circuit board upon which the package is to be mounted typically has formed on its surface a corresponding array of conductive pads which are aligned with the conductive contact lead elements of the package for electrically mounting the package on the target board. The target board typically includes other conductive traces and elements which lead from the array of conductive pads used for mounting the package to other circuitry on the board for connecting various components mounted thereon.
Typically, to mount such a package to a target board, solder material (e.g., solder balls) is provided in a manner corresponding to the array of conductive pads on the target board. The package is positioned with the contact lead elements in contact with the solder material corresponding to the array of conductive pads on the target board. The resulting structure is then heated until the solder material is melted and fused to the contact lead elements of the package.
Such area efficient packaging, e.g., micro lead frame packages or micro ball grid array packages, provide a high density of terminals at a very low cost. Also, this packaging provides for limited lead lengths. The limited lead lengths may reduce the risk of damage to such leads of the package, may provide for higher speed product, etc.
Generally, circuit boards and/or components mounted thereon are tested by designers as the circuit boards are being developed. For example, for a designer to test a circuit board and/or a package mounted thereon, the designer must first electrically connect the package to the target circuit board (e.g., using solder balls).
As described above, this may include mounting the package on the target board and heating the solder material (e.g., solder spheres) to fuse the solder material to the contact lead elements of the package. Therefore, the package may be prevented from being used again. It is desirable for various reasons to use packaged device adapters for mounting the packages and reuse such packages after testing. For example, such device packages may be relatively expensive. Further, for example, once attached, the solder material and/or the contact lead elements (e.g., land pads) are not accessible for testing. In addition, it is often difficult to rework the circuit board with the packages soldered thereon.
Various adapters are available for use in electrically connecting a package to a target board for one or more purposes. For example, U.S. Pat. No. 6,533,589 to Palaniappa et al., entitled “Packaged Device Adapter Assembly,” issued 18 Mar. 2003; U.S. Pat. No. 6,394,820 to Palaniappa et al., entitled “Packaged Device Adapter Assembly And Mounting Apparatus,” issued 28 May 2002; U.S. Pat. No. 5,791,914 to Loranger et al., entitled “Electrical Socket With Floating Guide Plate,” issued 11 Aug. 1998; U.S. Pat. No. 4,460,223 to Brown et al., entitled “Cover For Chip Carrier Socket,” issued 17 Jul. 1984; U.S. Pat. No. 5,892,245 to Hilton, entitled “Ball grid Array Package Emulator,” issued 6 Apr. 1999; and U.S. Pat. No. 5,730,620 to Chan et al., entitled “Method And Apparatus For Locating Electrical Circuit Members,” issued 24 Mar. 1998, all describe various adaptors that are used for mounting or locating packaged devices. Many of such adaptors use mechanisms for applying force or pressure on the packaged devices such that electrical contact of the packaged device conductive pads (e.g., pads on the bottom surface of the device) to corresponding contacts (e.g., a conductive elastomer or other arrangement of conductive elements, or further target board conductive land pads) is achieved. However, the mechanisms for applying such a force, at least in many circumstances, may apply too little force leading to inadequate contact or too large a force resulting in potential damage to, for example, contacts, components of the adaptor, etc. For example, as shown in U.S. Pat. No. 6,533,589 to Palaniappa et al., a screw or actuator element is used to apply a force to a floating member which is in direct contact with the packaged device to achieve adequate contact between contact pads of the packaged device and a conductive elastomer layer. In one or more cases, the actuator element or screw may be over tightened.